Metal roof structures typically comprise a series of parallel rafter beams extending across the building in one direction and purlin beams parallel to each other mounted on top of the rafters extending in a direction normal to the rafters. The purlins are often joined together by support bracing or straps for extra support. Insulation material in long sheets is placed in the area between purlins. The sheets of insulation material can be laid along the length of the purlins or across the purlins in a direction normal to the purlins. Hard roofing material such as metal decking is then attached on top of the purlins over the insulation material. Because the hard roofing material comes in long sheets and the roofs generally have two sloped sections, it is customary to construct along the width of the sloped section and then proceed along the length of the structure from one end to the other. The workers stand on the previously laid section of roof to construct the next section.
The insulation material must be supported between the purlins, and various methods of support have been used. Mounting straps or wire mesh that are attached to the purlins by forming a lattice have been used. This is referred to as banding. A sheet, typically made of vinyl and acting as a vapor barrier, is then rolled onto the lattice, and insulation material is placed between adjacent purlins and over the sheet. If the installation of the lattice is done from underneath the roof structure, scaffolding or lifting equipment is required.
Some systems dispense with the lattice and use the sheet itself to support the insulation material. The support sheet is draped from the adjacent purlins and the insulation material is placed on top of the support sheet. A carriage is used to aid in the dispensing of the support sheet. The carriage is positioned on top of the purlins and travels the length of the purlins during the roof construction. A roll of the support sheet material is mounted on the carriage and the support sheet is dispensed from the roll and placed on top of the purlins. As the carriage travels the length of the purlins the support sheet is draped across the purlins.
Wind can hinder or even prevent the workers from building the roof structure because of the handling of the large strips of insulation and roof decking. Because the roof is elevated from the ground level, the velocity of wind is generally greater and can cause problems for the workers constructing the roof. Even light winds which blow across or through the purlin support structure can disturb the insulation by causing the insulation material to lift up or shift positions after the workers have laid the insulation down in its proper installation position. For strong winds, it can be nearly impossible to handle the insulation and keep it in position before the hard roofing material is attached to the purlins.
Strong winds are also a safety concern for the workers on the top of the roof structure. A known safety feature for workers constructing a purlin type roof structure is to provide a platform which is movable along the tops of the purlins and which provides fall protection for the workers to prevent them from falling off the leading edge of the previously completed section of roof.
It would be desirable to have a method of building a roof structure which provides for wind protection and which is convenient and efficient.